s = 0
'''

'''
for i in '北京欢迎你':
    if i == '欢':
        break
    print(i)
else:
    print('循环结束')

for i in range(3):  # (2)条件判断
    print('当前i为：', i)
    # (3)语句块
    user_name = input('请输入用户名：')
    password = input('请输入密码：')
    if user_name == 'admin' and password == '123456':
        print('登陆成功')
        break
    elif i < 2:
        print('用户名或密码错误，您还有', 2 - i, '次机会')

else:  # while...else...
    print('输入错误次数过多，请稍后再试')
